Most big box stores and lighting stores have or can get them. Depends on what you are looking for. I use 4′ florescent bulbs on some plants, some get what looks like a standard flood bulb in a regular lamp, and then you get into the grow op type of lamps. And yes they sell them as well. Find out what spectrum of light you need and go with whatever is easier.

Special "grow lights" are a waste of money. Use standard fluorescent bulbs or tubes. The tubes require a special fixture, but compact fluorescent flood lights are available at Home Depot and can be screwed into regular incandescent fixtures.

Fluorescent light is in the spectral range required or most indoor plants and they are inexpensive to keep on for 8 hours per day because they use little energy.